1. Field of the Invention
The present invention relates to a technique of causing ink droplets to be ejected on a printing medium, so as to print an image. More specifically the present invention pertains to a technique of accurately monitoring a residual quantity of ink remaining in an ink reservoir that stores the ink therein.
2. Description of the Related Art
Printers that cause ink droplets to be ejected on a printing medium to print an image are widely used as an output device of various images output from a computer or the like. Such a printer uses the ink stored in an ink reservoir to eject ink droplets, and thereby can not print an image after the ink in the ink reservoir is used up.
Some techniques have accordingly been developed to monitor the residual quantity of ink in the ink reservoir. One of such techniques installs a sensor in the ink reservoir to monitor the residual quantity of ink. This technique with the sensor enables the residual quantity of ink to be monitored directly. Another known technique multiplies the number of ink droplets ejected by a weight of a single ink droplet measured in advance, so as to calculate the amount of ink consumption, and estimates the residual quantity of ink in the ink reservoir from the calculated amount of ink consumption. Since the printer ejects ink droplets under the control of the computer, it is easy to count the total number of ink droplets ejected with the control computer. This technique enables the residual quantity of ink in the ink reservoir to be monitored without any specific sensor.
When this known technique is applied to monitor the residual quantity of ink, there may be a significant difference between the actual remaining quantity of ink and the calculated remaining quantity of ink. As is known by those skilled in the art, the size of an ink droplet ejected from a nozzle depends upon the viscosity of the ink. One proposed technique takes into account a change of the viscosity according to the temperature of the ink, in order to improve the accuracy of calculating the residual quantity of ink. This proposed technique can not, however, attain the sufficient accuracy.
The object of the present invention is thus to precisely estimate an amount of ink consumption and thereby monitor a residual quantity of ink remaining in an ink reservoir with high accuracy.
At least part of the above and the other related objects is attained by a printer having an ink jet head that ejects ink droplets and an ink reservoir that has a predetermined capacity to store ink, wherein the ink jet head ejects ink droplets to create ink dots on a printing medium and thereby print an image on the printing medium. The printer includes: a supply condition detection unit that detects an ink supply condition, where an ink droplet ejected from one nozzle affects a supply of ink to another nozzle due to the structure of the ink jet head; an ink ejecting number counter than counts an ink ejecting number ejected by the ink jet head; and a residual ink quantity monitor that monitors a residual quantity of ink remaining in the ink reservoir by taking into account the ink supply condition detected by the supply condition detection unit, based on the ink ejected number counted by the ink ejected number counter and the predetermined capacity of the ink reservoir.
The present invention also provides a method of monitoring a residual quantity of ink, which corresponds to the printer of the present invention discussed above. Namely the present invention is directed to a method of monitoring a residual quantity of ink remaining in an ink reservoir, wherein the method is applied for a printer having an ink jet head that ejects ink droplets and the ink reservoir that has a predetermined capacity to store ink, and the ink jet head ejects ink droplets to create ink dots on a printing medium and thereby print an image on the printing medium. The method includes the steps of: (a) detecting an ink supply condition, where an ink droplet ejected from one nozzle affects a supply of ink to another nozzle due to the structure of the ink jet head; (b) counting an ink ejecting number ejected by the ink jet head; and (c) monitoring a residual quantity of ink remaining in the ink reservoir by taking into account the ink supply condition detected in the step (a), based on the ink ejected number counted in the step (b) and the predetermined capacity of the ink reservoir.
The printer or the corresponding method of the present invention detects the ink supply condition relating to the supply of ink and counts the number of ink droplets ejected by the ink jet head. The structure takes into account the detected ink supply condition and monitors the residual quantity of ink in the ink reservoir based on the count of the ink ejecting number and the predetermined capacity of the ink reservoir. The amount of ink ejected from the ink jet head depends upon the ink supply condition. This arrangement of the present invention monitors the residual quantity of ink while taking into account the ink supply condition, thereby enabling the residual quantity of ink remaining in the ink reservoir to be monitored with high accuracy.
In the printer and the corresponding method of the present invention, the weight of a single ink droplet measured in a specified state of the ink supply condition may be stored in advance as a unit amount of ink. In the process of printing an image, the procedure first detects the ink supply condition relating to the supply of ink and counts an ink ejecting number within a preset time period. The procedure then multiplies the count of the ink ejecting number by the measured weight of a single ink droplet while taking into account the detected ink supply condition, and determines the ejecting amount of ink within the preset time period. The ink ejecting number may be a number of ink droplets actually ejected by the ink jet head or any suitable variable that is readily counted and is convertible to the number of ink droplets. The procedure subsequently accumulates the ejecting amount of ink thus determined to give a cumulative amount of ink ejection and monitors the residual quantity of ink remaining in the ink reservoir based on the cumulative amount of ink ejection and the predetermined capacity of the ink reservoir. The arrangement of taking into account the ink supply condition enables the precise calculation of the ejecting amount of ink and thereby enables the residual quantity of ink remaining in the ink reservoir to be monitored with high accuracy.
In accordance with one preferable modification, the printer stores the volume of a single ink droplet as the unit amount of ink, instead of the weight of a single ink droplet. In the process of printing an image, the procedure detects the ink supply condition and counts the ink ejecting number within the preset time period. The procedure then calculates the ejecting amount of ink within the preset time period from the stored volume of a single ink droplet and the count of the ink ejecting number while taking into account the detected ink supply condition, and accumulates the ejecting amount of ink thus determined to monitor the residual quantity of ink remaining in the ink reservoir. This structure calculates the ejecting amount of ink while taking into account the ink supply condition. This enables the ejecting amount of ink to be calculated precisely and thereby improves the accuracy of monitoring the residual quantity of ink.
The following technique is preferably applicable to take into account the effect of the ink supply condition in the process of calculating the ejecting amount of ink within the preset time period. The technique stores in advance adequate correction coefficients corresponding to a variety of ink supply conditions. The procedure multiplies the weight of a single ink droplet, the count of the ink ejecting number within the preset time period, and the correction coefficient corresponding to the detected ink supply condition. This arrangement corrects a variation in weight of a single ink droplet according to the change of the ink supply condition and enables the ejecting amount of ink within the preset time period to be calculated with high accuracy.
Another preferable application stores the weight of a single ink droplet ejected in each state of the ink supply condition corresponding to the each state of the ink supply condition, in place of the weight of a single ink droplet ejected in the specified state of the ink supply condition. The ejecting amount of ink within the present time period is calculated by multiplying the count of the ink ejecting number by the weight of a single ink droplet corresponding to the detected state of the ink supply condition. This arrangement also enables the ejecting amount of ink to be calculated with high accuracy by taking into account a possible variation in size of the ink droplet according to the ink supply condition.
In the printer of the present invention, it is preferable that the temperature of the ink supplied to the ink jet head is measured as the ink supply condition. The measurement of the temperature of ink enables the ejecting amount of ink to be calculated by taking into account the fact that an increase in viscosity of ink prevents a smooth supply of ink to the ink jet head. This arrangement accordingly improves the accuracy of monitoring the residual quantity of ink remaining in the ink reservoir.
It is also preferable that the ink supply condition is defined as a change of a condition with time accompanied by the ejection of ink droplets; for example, the residual quantity of ink in the ink reservoir or the cumulative ink ejecting number. The detection of such conditions enables the ejecting amount of ink to be calculated by taking into account the fact that the size of the ink droplet is affected by the residual quantity of ink in the ink reservoir and the increased viscosity of the ink over a long time period. This arrangement accordingly improves the accuracy of monitoring the residual quantity of ink remaining in the ink reservoir.
It is further preferable that a condition depending upon the composition of ink is detected as the ink supply condition. The condition depending upon the composition of ink may be a simple condition, such as the product number of ink representing the type of ink, as well as the types of the solvent and dye in the ink and its mixing ratio. The composition of ink generally depends upon the type of ink. The detection of the condition depending upon the composition of ink enables the ejecting amount of ink to be calculated by taking into account the fact that the ink supply condition, such as the viscosity of ink, is varied with a variation in composition. This arrangement accordingly improves the accuracy of monitoring the residual quantity of ink remaining in the ink reservoir.
In accordance with another preferable application of the present invention, the amount of ink to be supplied to the ink jet head may be determined as the ink supply condition. As described previously, the size of the ink droplet ejected is affected by the supply of ink fed to the ink jet head. The structure of determining the amount of ink to be supplied to the ink jet head and calculating the ejecting amount of ink based on the result of the determination enables the residual quantity of ink in the ink reservoir to be monitored with high accuracy.
In the printer where the ink jet head ejects ink droplets to print an image while changing the relative position to the printing medium, it is preferable that a preset printing resolution is detected as the ink supply condition. The printing resolution here is an index representing a distance between adjoining ink dots created on the printing medium when the ink jet head successively ejects ink droplets while changing the relative position to the printing medium. A typical index representing the printing resolution is dpi, that is, a number of ink dots that can be created per inch. For example, the printing resolution of 720 dpi means that 720 ink dots may be created per inch. In such a printer, the printing resolution may be changed according to the desired printing quality and printing speed. The higher printing resolution may increase the number of ink droplets ejected per unit time. This leads to a shortage of the ink supply and causes smaller ink droplets to be ejected. Because of the relationship between the printing resolution and the size of the ink droplet, the detection of the printing resolution as the ink supply condition readily improves the accuracy of calculation of the ejecting amount of ink and enables the residual quantity of ink in the ink reservoir to be monitored with high accuracy.
In such a printer, it is also preferable that a recording mode is detected as the ink supply condition. The recording mode here represents the number of relative movements of the ink jet head to the printing medium required to complete one raster line. The raster line means a line of ink dots formed when the head ejects ink droplets while changing the relative position to the printing medium. In the case where a high printing quality is required, the printer may form one raster line by a plurality of relative movements of the ink jet head to the printing medium, instead of one relative movement. Printing one raster line by a plurality of scans naturally reduces the number of ink droplets ejected in each scan. Printing one raster line by one scan, on the other hand, increases the number of ink droplets ejected within a short time period. This causes small ink droplets to be ejected. The structure of detecting the recording mode as the ink supply condition thus readily improves the accuracy of calculation of the ejecting amount of ink.
In accordance with still another preferable application of the present invention, a dot pattern, which is an arrangement of ink dots formed on the printing medium, may be detected as the ink supply condition. This arrangement enables the ejecting amount of ink to be calculated by taking into account the fact that the size of the ink droplet ejected is affected by the dot pattern. This accordingly enables the residual quantity of ink in the ink reservoir to be monitored with high accuracy.
It is preferable that a relative driving frequency is detected as the dot pattern. The relative driving frequency here is an index representing the time-based frequency at which each nozzle ejects ink droplets. The concrete definition is given below. It is assumed that a certain nozzle ejects ink droplets to create dots while moving on the printing medium. A certain dot created on the printing medium is specified as a target dot. In the case where a dot has been created immediately before the target dot, that is, when dots are successively created, the relative driving frequency of the target dot is defined as 100%. In the case where no dot has been created immediately before the target dot and an adjoining dot is apart from the target dot by the interval of one dot, the relative driving frequency of the target dot is defined as 50%. In a similar manner, in the case where an adjoining dot is apart from the target dot by the interval of two dots, the relative driving frequency of the target dot is defined as 33%. In the case where an adjoining dot is apart from the target dot by the interval of three dots, the relative driving frequency of the target dot is defined as 25%. The size of the ink droplet ejected from the nozzle is varied with a variation in relative driving frequency of the dot formed by the ink droplet. The detection of the relative driving frequency as the dot pattern thus enables the ejecting amount of ink to be calculated by taking into account this factor and thereby improves the accuracy of monitoring the residual quantity of ink remaining in the ink reservoir.
In the printer having the ink jet head that can simultaneously create a plurality of ink dots, it is preferable that a driving duty is detected as the dot pattern. The driving duty here is an index representing a ratio of the number of ink dots created simultaneously to the number of ink dots that can be created simultaneously by the ink jet head. The concrete definition is given below. It is here assumed that 48 dots can be created simultaneously on the printing medium. When 12 dots are created simultaneously, the driving duty is defined as 25%. When 24 dots are created simultaneously, the driving duty is defined as 50%. The size of the ink droplet ejected from the nozzle is affected by the driving duty. The structure of calculating the ejecting amount of ink by detecting the driving duty and taking into account this factor accordingly enables the residual quantity of ink in the ink reservoir to be monitored with high accuracy.
In such a printer, it is also preferable that the number of ink dots created simultaneously is determined to be greater than a preset value (first recording condition) or not greater than the preset value (second recording condition) as the dot pattern. The size of the ink droplet is also varied according to the difference of the recording condition. The structure of calculating the ejecting amount of ink by taking into account this factor accordingly enables the residual quantity of ink in the ink reservoir to be monitored with high accuracy.
A plurality of ink dots that can be created simultaneously may be divided into a plurality of groups, based on a specific relationship. In this case, it is preferable that the driving duty is detected for each group.
The following describes the division of the plurality of groups based on the specific relationship. By way of example, in the printer having a plurality of ink chambers, some of the adjoining ink chambers may receive supplies of ink via an identical ink supply conduit, because of some manufacturing reasons. One applicable technique for ejecting ink droplets drives an actuator to vibrate a vibrating plate, which defines a top plate of the ink chamber, and thereby causes ink droplets to be ejected. Because of some manufacturing reasons, one long vibrating plate may form a common top plate of the adjoining ink chambers. In such cases, the ink chambers having the common ink supply conduit or the ink chambers having the common vibrating plate are included in the same group.
One available arrangement counts the ink ejecting number within the preset time period with respect to each group and calculates the ejecting amount of ink from the ink ejecting number and the weight of a single ink droplet while taking into account the driving duty of each group. This arrangement improves the accuracy of calculation of the ejecting amount of ink and thereby enables the residual quantity of ink in the ink reservoir to be monitored with high accuracy.
In accordance with one preferable application of the present invention, the mechanism for ejecting ink droplets has an optical sensor that measures the intensity of reflected light from the printing medium. The optical sensor may be used to detect an arrangement of ink dots actually formed on the printing medium. This arrangement enables the ejecting amount of ink to be calculated by taking into account the difference in arrangement of ink dots actually formed on the printing medium, thereby further improving the accuracy of monitoring the residual quantity of ink in the ink reservoir.
The following arrangement may be adopted in the printer having the ink jet head that can eject at least two different types of ink droplets having different sizes. The arrangement stores in advance the weight of each type of ink droplet possibly created. The arrangement counts the ink ejecting number within the preset time period and calculates the ejecting amount of ink with respect to each type of ink droplet. The procedure may sum up the ejecting amounts of ink within the preset time period for the respective types of ink dots and accumulate the total ejecting amount of ink. In the printer that can eject at least two different types of ink droplets having different sizes, this arrangement precisely calculates the ejecting amount of ink and enables the residual quantity of ink in the ink reservoir to be monitored with high accuracy.
Another possible procedure stores the weight of a single ink droplet, for example, only for the smallest ink dot and relative factors to the smallest ink dot for the other ink dots. This procedure counts the ink ejecting number within the preset time period as the ink ejecting number corresponding to the smallest ink dots formed on the printing medium. The ejecting amount of ink may be calculated from the count of the ink ejecting number and the weight of ink for the smallest ink dot. In the printer that can create at least two different types of ink dots having different sizes, this arrangement improves the accuracy of calculation of the ejecting amount of ink and enables the residual quantity of ink in the ink reservoir to be monitored with high accuracy. This procedure favorably simplifies the process of calculation, compared with the above procedure that separately calculates the ejecting amount of ink for each type of ink dot and then sums up the ejecting amounts of ink.
The following arrangement may be adopted to monitor the residual quantity of ink for each color in the printer that has an ink reservoir storing a plurality of inks having various colors and causes ink droplets of the various colors to be ejected to create ink dots of the various colors on the printing medium. The arrangement counts the ink ejecting number within the preset time period for each color, and calculates the ejecting amount of ink for each color from the count of the ink ejecting number for each color and the weight of a single ink droplet. The arrangement accumulates the ejecting amount of ink to give a cumulative amount of ink ejection with respect to each color and monitors the residual quantity of each color ink in the ink reservoir based on the cumulative amount of ink ejection and a predetermined capacity of each color ink. In the printer that can create ink dots of various colors with the various color inks, this arrangement precisely calculates the ejecting amount of ink for each color ink and enables the residual quantity of each color ink in the ink reservoir to be monitored with high accuracy.
In accordance with another preferable application of the present invention, an alarm may be given when the difference between the cumulative amount of ink ejection and the predetermined capacity of the ink reservoir becomes not greater than a predetermined value. The alarm may be an alarm lamp, a buzzer, or a message displayed on the CRT. The operation of xe2x80x98giving an alarmxe2x80x99 includes not only that the printer directly gives an alarm to the user but that the printer gives an alarm to another apparatus, for example, a computer that controls the printer. The degree of alarm may be changed according to the magnitude of the difference. For example, the color of the alarm lamp or the sound of the buzzer may be changed according to the magnitude of the difference. The structure of giving an alarm facilitates the monitor of the residual quantity of ink in the ink reservoir. Here the only requirement for giving an alarm is that the difference between the cumulative amount of ink ejection and the predetermined capacity of the ink reservoir substantially becomes not greater than a predetermined value. By way of example, when the ratio of the cumulative amount of ink ejection to the predetermined capacity of the ink reservoir becomes not less than a preset level, it may be determined that the difference substantially becomes not greater than the predetermined value.
Another available arrangement informs the user of the ratio of the cumulative amount of ink ejection to the predetermined capacity of the ink reservoir in the form of a digital or analogous display. For example, a specific display mounted on the printer or the screen of the computer for controlling the printer may be used to give such information. This arrangement further facilitates the monitor of the residual quantity of ink in the ink reservoir.
Any other suitable method for the printer may be applied to give an alarm or information. One possible method shows how many A4 printing sheets can be printed with the residual quantity of ink. The application of the suitable method for the printer facilitates the monitor of the residual quantity of ink in the ink reservoir.
In the printer that carry out head maintenance operations, which force the ink jet head to eject ink droplets, in order to maintain the ejecting state of ink droplets, the type of the head maintenance operation may be detected as the ink supply condition. There may be a variety of head maintenance operations. For example, the head maintenance operation may be carried out to prevent the ejecting state of ink droplets from being worsened or to recover the worsened ejecting state of ink droplets. The latter includes the operations to recover the slightly worsened ejecting state and the significantly worsened ejecting state. The size of the ink droplet forcibly ejected depends upon the type of the head maintenance operation. Detecting the type of the head maintenance operation accordingly enables the ejecting amount of ink during the head maintenance operation to be calculated with high accuracy, thereby improving the accuracy of monitoring the residual quantity of ink. One modified structure carries out the detection of the ink supply condition and the count of the ink ejecting number during the head maintenance operation and accumulates the ejecting amount of ink. This arrangement also improves the accuracy of monitoring the residual quantity of ink.
The method of monitoring the residual quantity of ink according to the present invention may be attained by combining a printer that ejects ink stored in the ink reservoir with a computer that controls the printer and causing the computer to carry out predetermined processes, such as counting the ink ejecting number. One possible application of the present invention is accordingly a recording medium, in which a program for carrying out the predetermined processes is stored in a computer readable manner. Namely the present invention is directed to a recording medium, in which a program for monitoring a residual quantity of ink remaining in an ink reservoir is recorded in a computer readable manner. The program is applied for a printer having an ink jet head that ejects ink droplets and the ink reservoir that has a predetermined capacity to store ink, wherein the ink jet head ejects ink droplets to create ink dots on a printing medium and thereby print an image on the printing medium. The program causes a computer to carry out the functions of: detecting an ink supply condition, which affects a supply of ink to the ink jet head; counting an ink ejecting number ejected by the ink jet head; and monitoring a residual quantity of ink remaining in the ink reservoir by taking into account the detected ink supply condition, based on the count of the ink ejecting number and the predetermined capacity of the ink reservoir.
The computer reads the program stored in such a recording medium and carries out the required processes including the detection of the ink supply condition, the count of the ink ejecting number, and the monitor of the residual quantity of ink. This arrangement enables the residual quantity of ink remaining in the ink reservoir to be monitored with high accuracy by taking into account a variation in ink supply condition.
One preferable application of the printer according to the present invention corrects the count of the ink ejecting number according to the ink supply condition and monitors the residual quantity of ink remaining in the ink reservoir based on the corrected ink ejecting number and the predetermined capacity of the ink reservoir. The concrete arrangement of this application is discussed below.
The structure of this application measures an ink weight of a unit ink ejecting number under a preset condition (reference condition), divides the predetermined capacity of the ink reservoir by the measured ink weight to calculate a factor, and stores the factor as a preset value corresponding to the predetermined capacity of the ink reservoir. Namely the factor represents the ratio of the ink weight corresponding to the ink ejecting number under the reference condition to the predetermined capacity of the ink reservoir. In the process of printing an image, this structure counts the ink ejecting number while carrying out the correction according to the ink supply condition. The residual quantity of ink remaining in the ink reservoir is monitored using the corrected count of the ink ejecting number and the preset value stored in advance. This arrangement enables the residual quantity of ink to be monitored with high accuracy by taking into account a change of the ink supply condition.
These and other objects, features, aspects, and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments with the accompanying drawings.